General Model Output Discussion:

[Iceberg]

A bit of pure IMBY from me.

I've plotted the GFS, METO and ECM pressure on the latest 06Z pressure Ensembles for Dorset.

The 3 red dots are, top METO 00Z run, middle GFS 00Z run and bottom 00Z ECM run.

It's not perfect, but essentially out of the 00Z's ECM made the most of some wintry precip coming up from the south, for the southern coast districts for Monday/Tuesday.

UKMETO didn't really but did bring it into the very far SW (as mentioned by Ian).

GFS 06Z as we all know went well overboard on the LP, but did perhapes pick up on a signal, but then failed miserably to execute it (very common with GFS IMO).

The 12Z's should IMO make more of the feature for the South coastal counties, and the 850's from the ECM show that it will be plenty cold enough for it to all fall as snow, providing the rain band doesn't get further north than the M4.

Beyond 168 and I am sure the models will present there normal range for possible outcomes (some good some bad), but for me the key timeframe will be 120-144Z.

[Guest North Sea Snow Convection]

Several points here, firstly its no good getting hung up on individual model runs, of course model runs are there to be commented on, but some members insist on taking each one as literal, they are all subject to change. If I have to read another post complaining about the lack of snow for their area I might just scream, comment by all means but stop the moaning. Secondly in regards people getting mislead by other members posts, I have to say mainly this is the fault of the reader. I can recall several posts regarding the degree of cold we might expect if some model runs were to come to fruition, I don't remember many members claming to see masses of snow potential, that again is down to members interpreting very cold as very snowy, if you don’t understand what is meant, ask. Comments claiming, if this had happened in the 60s, 70s, 80s we would have had masses of snow, are just plain wrong, I can recall a fair few cold winters that were not snowy and plenty with spells like this one, very marginal with a real wintry mix. Last point, be careful who you listen to, there are some good posters on this thread and there are a couple whose reputation is IMO not deserved. Just because a poster predicts cold and sounds like they know what they are talking about, does not mean they do or that they are being completely objective.

Your suggestions there are good one's and the perspective is right too

Following up Icebergs interesting analysis below, I would agree that it might well be the case that the 12z's a whole suggest a northward extent of the ppn and perhaps even the Lp system itself as it tracks to our south. Not just from an IMBY perspective, but for the nation as a whole it is important that we don't see any trend towards 'lifting out' the cold from the south and south west. The models in the last 24 hrs have trended the protecting northern block slightly eastwards and in turn come away from the rather more west based -NAO. We don't want to see any trend back towards that. Worth pointing out before people start to go ga-ga if they see the GFS continue 'off on one' in the 12z output.

I still think (and hope) that the trend started from the 12's last night and consolidated in style again this morning will be maintained - but we should be prepared, as is often the case with the models for another deviation from this script (even if it isn't the right one) at some stage. That might happen this evening - but might not happen at all of course - but just a word to stop any wrist slitting posts if it does lol!

[nick sussex]

Theres alot of talk about the ukmo further outlook today in here, given the synoptics on show across the board it seems like a fair call, of course the ukmo are going to highlight more eastern areas as the wind flow looks to be often ne to east this doesn't mean however that other areas won't see anything, the longer you can hang onto the cold the more chance there is of the odd suprise being thrown up.

In terms of some of the NIMBYISM in here, i can understand it to a point that of course people want to see snow falling in their location but some of the remarks about the model output have been just laughable.

Also just like to say a good post from weather eater which i agree with, sometimes people think cold and definite snow but as we've seen it just doesn't always happen like that,but you certainly can't get snow without the cold first !

I wonder whether there can be a throwing toys out of the pram thread so then people who want an idea of whats going on can look in this thread and not have to trawl through endless whining posts and those that want to blow off some steam can do it there!

Oh i forgot there is one already called the whining thread so perhaps that can be pinned so it's always at hand in case of emergencies :smiliz46: !

[Bristawl Si]

Your suggestions there are good one's and the perspective is right too

Following up Icebergs interesting analysis below, I would agree that it might well be the case that the 12z's a whole suggest a northward extent of the ppn and perhaps even the Lp system itself as it tracks to our south. Not just from an IMBY perspective, but for the nation as a whole it is important that we don't see any trend towards 'lifting out' the cold from the south and south west. The models in the last 24 hrs have trended the protecting northern block slightly eastwards and in turn come away from the rather more west based -NAO. We don't want to see any trend back towards that. Worth pointing out before people start to go ga-ga if they see the GFS continue 'off on one' in the 12z output.

I still think (and hope) that the trend started from the 12's last night and consolidated in style again this morning will be maintained - but we should be prepared, as is often the case with the models for another deviation from this script (even if it isn't the right one) at some stage. That might happen this evening - but might not happen at all of course - but just a word to stop any wrist slitting posts if it does lol!

With regards the LP system progged for Sunday/Monday it wouldn't surprise me to see that disappear into northern France over the next few runs. Ian, on the SW thread did strike a note of caution on that development.

[VillagePlank]

I see the METO have decided to go with the flow with their updated winter forcast. Their long range views on things have changed quite starkly!

Yes, a stark change in about 5 weeks. Still, nearly everyone got it wrong this time, around so they're in good company.

Anyway, the Southern part of Britain, it seems to me, is entirely dependent on the track of that low. The 6z was a mild outlier and in the light of other models, and runs by even itself, it should be well and truly binned.

Therefore, if the low is too far North (I think that it is) then the Theta W values of less than 2C (snow-fest trigger!) should encompass the whole of the UK for a week.

As for precipitation, I think the New Year is likely to start off with snowfall, end the first week with snowfall, and be fairly dry in between leading to monster frosts, freezing fog, etc etc.

Into the medium term and the part that interests me is that weaker more northerly part of the jet-stream (over Iceland in chart) ...

This gets stronger for a time before dissipating leaving us with a moderate but very flat jet-stream very far south of where it has been in recent times (2008 excluded, of course):

What this suggests to me is that the centres of cyclogenesis will be NE Newfoundland, E New York, W Spain, and SE Europe - which strongly points to the medium future holding out for a strong Scandinavian high, as the Greenland high fills the low pressures to it's south and south west. The models don't support this view, yet.

The GFS supports this in a somewhat 2/3rds fashion ...

The Atlantic 'block' recedes as the GH loses it's strength, and low pressure forms readily all over Europe - but the utter surprise is that there is no Scandinavian high. Why this is, is perhaps why this 6z run is completely out on it's own and is a mild outlier.

Just feels wrong, if you know I mean. Still, better luck with the 12z! My bet is on a Scandy high.

Edited December 30, 2009 by VillagePlank

[wysiwyg]

A bit of pure IMBY from me.

Nothing IMBY about that at all imo. To me it's a well put together analysis that shows that the latest GFS 06Z run is trending towards the favoured (by NOAA) ECM predictions.

Just a side note to put all the model predictions into perspective. Technically they are all "FI" (for want of a better term) even before the start button is pressed. None of the input data will be synchronised in time, variations will occur due to time shifted samples, obscured readings (particularly satellite and airborne). Again, we see ensembles diverging widely after only 4-5 days indicating that the extrapolation that these models predict is currently highly sensitive to minor variations in initial data. These errors multiply rapidly as the iterations progress so, for example, if snow fall is predicted at T+x and doesn't occur, then the remainder of the run is severely compromised due to inaccurate surface temperature modelling.

I think it's worth also re-iterating (during the wait for the 12zs) that there is a whole host of other info on here that is objective and gives a pretty good summary of the outlook. If we start being too agressive with off-topic posts in this thread then no-one will ever ask questions or present their own analyses. In other words there has to be some tolerence of different views and differing levels of understanding of the models and the interpretation associated with their output.

Enjoy the synoptics though - they are rare for winter :smiliz46:

[aspire27]

Are todays model outputs still showing the epic cold for Januray 1st S.Murr and others was talking about?

[woldsowl]

Also just like to say a good post from weather eater which i agree with, sometimes people think cold and definite snow but as we've seen it just doesn't always happen like that,but you certainly can't get snow without the cold first !

Hi Nick.

Don't want to disagree completely with you, but there have been a number of posts here recently referring to "you can't get snow without the cold first".

Depends how you define the cold, but I have recorded many instances of warm to snow to cold in recent years, particularly when living in Penistone at 200m South Pennines.

Yesterday/todays event "could" have been another example, but for the sake of a degree or half, of this occurring again, with relatively mild weather, rain to snow, followed by cold air sinking.

Maybe it's more common in slightly higher locations, but I would never dismiss this scenario. :smiliz46:

[Mark Parsons]

Several points here, firstly its no good getting hung up on individual model runs, of course model runs are there to be commented on, but some members insist on taking each one as literal, they are all subject to change. If I have to read another post complaining about the lack of snow for their area I might just scream, comment by all means but stop the moaning. Secondly in regards people getting mislead by other members posts, I have to say mainly this is the fault of the reader. I can recall several posts regarding the degree of cold we might expect if some model runs were to come to fruition, I don't remember many members claming to see masses of snow potential, that again is down to members interpreting very cold as very snowy, if you don’t understand what is meant, ask. Comments claiming, if this had happened in the 60s, 70s, 80s we would have had masses of snow, are just plain wrong, I can recall a fair few cold winters that were not snowy and plenty with spells like this one, very marginal with a real wintry mix. Last point, be careful who you listen to, there are some good posters on this thread and there are a couple whose reputation is IMO not deserved. Just because a poster predicts cold and sounds like they know what they are talking about, does not mean they do or that they are being completely objective.

My list of members, who I pay special attention to, goes like this

John Holmes

Steve Murr

Glacier point

Nick Sussex

T W S

Kold Weather

Others include

NSC (Tamara)

TEITS

Ian Ferguson

Pyrotech

Ian Brown

And a few others

Totally agree mate.

[Geordiesnow]

I also don't see what the worry is in truthness, the trend is still there at least.

Hopefully the GFS can place that low further South than it has on the 06Z as it has been said, it increases our chances for a more widespread snowy spell. Anyways, for those worrying about the 06Z, if it showed a really cold easterly, would we say more runs are needed and its far from nailed? I would of thought so.

enjoy the cold and for some lucky few(including me), enjoy the snow showers we may get in the next day or two!

[Thundery wintry showers]

Looking at the current model outputs, the phrase "people are never satisfied" springs to mind- it's like in summer, where many people wish for heat, sun and thunderstorms, and then when we get them we get a cascade of posts complaining that it's too hot. Here, we have people wishing for cold snowy synoptics and when we get them, complaining that it might not snow in their given areas of the country.

It is clear that the GFS keeps taking low pressure systems further north than the ECMWF. The effect is that southern areas get more frontal precipitation and therefore more chance of snow in central and western parts of the Midlands and south, but it always makes it a knife edge situation because if the bands get too far north, the cold air gets mixed out and many places get rain.

The low pressure to the south also hinders the prospect of a cold north-easterly setting in as per the ECMWF- and that means a drier easterly for Scotland and northern England with not many snow showers moving in off the North Sea. In contrast I would expect a large number of snow showers to affect eastern districts, perhaps penetrating to some western at times, if the ECM verifies, particularly with those NE'lys from T+168 onwards.

So, if it's snow events you're after, the lows tracking further north may be good news if you live in some western, southern and central parts of England that are sheltered from North Sea convection. For other parts of the country you'd be better off seeing those lows further south and allowing cold NE'lys in bringing plenty of convection off the North Sea as per the ECM. Personally I think the ECM may be overdoing those NE'lys but I expect it to be closer to the mark than GFS.

[TEITS]

Hi TEITS,

I think you better go check the update from Met Office.

Nothing to ramp about - If you like it dry - Then sure.

Looks like turning very cold though

Just have and its fantastic, heavy prolonged snow showers and remaining very cold till day 15!

However let me clear something up with regards to the models and the Met O outlook. There is no way any model at this range will be able to properly model convection if a NNE/NE,ly is on its way. Furthermore because of the timeframe we don't know if it will be a N/NNE/NE/ENE,ly. All of these would spread the distribution of snow showers differently.

Also there is something else that members who live in areas such as W Midlands/NW England/Wales etc need to take into account. Our coldest weather generally comes via a NE/E,ly so it stands to reason E areas will see the heaviest snow. This has always been the case and always will be. For the locations I mention you need either fronts meeting the cold air or troughs from the E pushing well inland.

At the moment we should just concentrate on the overall pattern and see if the LP does track to the S of the UK and the Greenland block remains in situ. Only then can we begin looking at whether an N/NE,ly follows.

This is the 2nd GFS run to suggest this but a band of snow showers moving into E Midlands/E Anglia on Friday. Slight chance of a few light snow showers tomorrow night!

http://www.wetterzentrale.de/pics/Rmgfs513.gif

Edited December 30, 2009 by THE EYE IN THE SKY

[NorthNorfolkWeather]

Hi All,

there was a question regarding SST's this morning, which I didn't see an answer to.

I think the gist of the question was "Are the seas around us warmer now than they were in the 60's/70's?". Any takers on that?

Living, as I do, close to both the North and East Coast of Norfolk, I understand that the models usually have quite a large degree of uncertainty regarding convective showers dumping snow, can anyone here tell me what I should look at in terms of temps at 850mb to see what my risk of snow is?

I've been following the temperature variations on the rigs in the Southern North Sea and it is nowhere near as cold as it was a couple of weeks ago.

the temperature on 62144 is still almost 6C, I would expect that to drop quickly with very cold uppers.

[Iceberg]

12Z GFS out to T78 and a snow event for southern england looks to be coming up IMO. :)

Slightly different to the 06Z, but not massively so and looks to be keeping the low further south, all more realistic.

[Thundery wintry showers]

It's a long-established fact that prolonged cold spells in winter tend to have winds blowing from the north and east, snow showers peppering northern and eastern regions (and sometimes the south when we pick up an easterly), with marginal frontal rain/sleet/snow events affecting central and southern districts at times. Menawhile a large part of north-west England and west Wales and west Scotland, particularly near the west coast, tends to pick up just the odd flurry here and there.

For widespread snow in sheltered western areas you need more of an Atlantic influence, be it a frontal battleground with fronts aligned N-S pushing against continental air, or some sort of Irish Sea-related disturbance when northerlies take over- usually a polar low or a westerly component to the airflow bringing showers in from the Irish Sea. 20-23 December was a good example of the latter scenario. But this "northerly" scenario often relies upon a west based -ve NAO which can lead in the long run to milder weather coming up from the SW.

This is the main reason why snow cover frequencies are higher near the east coast than they are near the west coast. Western coastal areas rely upon synoptics for widespread snow events that are generally less sustainable for long periods and less cold.

Unfortunately for snow fans living in said sheltered western areas, the above will need to be taken into account when surveying these old-school cold synoptics. For eastern areas, a spell of cold and snowy weather is looking likely.

[damianslaw]

Gfs and ECM continue to show a different scenario as we head into the New Year, with ECM keen on pulling in a very cold north easterly feed, whereas GFS want to draw in a low pressure very much on a similiar path as the one that moved into the SW yesterday.

However, as GFS showed the current low to track further north than it has, I feel it is being again rather progressive as it always seems to do with any atlantic low, and that the ECM evolution is model to bank on, whether we see a very cold deep seated NE or more of a slacker north easterly flow with less chance of troughs developing and therefore a more drier picture away from the east coast remains to be seen.

Longer term, signs that a scandi high will develop as those heights to the NW eventually fill or indeed simply merge with heights to the NE, the outlook well into January remains a cold one.

[tinybill]

12Z GFS out to T78 and a snow event for southern england looks to be coming up IMO.

Slightly different to the 06Z, but not massively so and looks to be keeping the low further south, all more realistic.

http://www.meteociel.com/modeles/gfs/precipitations/30h.htm

snow for the east coast from new years eve then it looks like its staying very cold deep in to Jan with more snow to come here at the moment its pouring down!!!

[Iceberg]

12Z GFS out to T78 and a snow event for southern england looks to be coming up IMO.

Slightly different to the 06Z, but not massively so and looks to be keeping the low further south, all more realistic.

Heavy snow into the SW Sunday Afternoon, I'd take that thankyou very much.

I don't care what the rest of the run does,(although I think it will be good)

[Iceni]

Hi All,

there was a question regarding SST's this morning, which I didn't see an answer to.

I think the gist of the question was "Are the seas around us warmer now than they were in the 60's/70's?". Any takers on that?

Living, as I do, close to both the North and East Coast of Norfolk, I understand that the models usually have quite a large degree of uncertainty regarding convective showers dumping snow, can anyone here tell me what I should look at in terms of temps at 850mb to see what my risk of snow is?

I've been following the temperature variations on the rigs in the Southern North Sea and it is nowhere near as cold as it was a couple of weeks ago.

the temperature on 62144 is still almost 6C, I would expect that to drop quickly with very cold uppers.

I was swimming at Dunwich in June. I was amazed how warm and bath-like the sea was despite being early summer… then my husband mentioned Sizewell B discharging warmed water into it. In addition there's Dungeness as well. Might affect the sea temperatures.

[TEITS]

Heavy snow into the SW Sunday Afternoon, I'd take that thankyou very much.

I don't care what the rest of the run does,(although I think it will be good)

From +96 the LP should move E. Doubt it will move much further N due to hitting a brick wall. Having said this it is the GFS!

[Iceberg]

Completely agree Ian, the precip can't get above the M4 really, otherwise it starts to introduce too much marginality into it.

As it is the 12Z has 3 days of snow for the SW, accumulations of upto maybe 20cm's or so, very oldschool and I very much want the METO and ECM to follow suite.

TEITS, I hope that brick wall doesn't move.

[PB22]

The 12Z GME and UKMO do not make much of that low that the GFS wants to bring close to the south...instead we have to look northeast:

GME T+132: http://91.121.94.83/...n/gme-0-132.png

UKMO T+120: http://www.meteociel...20-21.GIF?30-17

I was swimming at Dunwich in June. I was amazed how warm and bath-like the sea was despite being early summer… then my husband mentioned Sizewell B discharging warmed water into it. In addition there's Dungeness as well. Might affect the sea temperatures.

OT: But there was snow on Sizewell beach last week.

Edited December 30, 2009 by Paul B

[nick sussex]

A much better gfs run so far compared to that nonsense that the gfs 06hrs run churned out, the block is better orientated here and is in line with the general guidance overall, again here though its very difficult to say how far north the precip will get. However this is a totally different scenario from the recent low, this is running into cold air embedded at the surface with the surface flow off a cold continent ahead of the low.

Interesting difference of opinion here with the ukmo,the ukmo looks guaranteed long term cold the gfs comes with more risk but also more snow initially. The 144hrs ukmo is great, personally if i was back in Sussex i'd forego that possible snow event for the UKMO which would lock in the cold and bring further snow later.

Edited December 30, 2009 by nick sussex

[Cumulonimbus Tower]

At least with the 12z gfs we are starting to get some consistency between it and the 00 ECM up to the 144h sort of range.

Edited December 30, 2009 by ned

[PB22]

A sensational UKMO 12z T+144 chart:

http://www.meteociel...44-21.GIF?30-17

Edited December 30, 2009 by Paul B